In code division multiple access (CDMA) communication systems, unnecessary and excessive transmission by a user may cause interference for other users in addition to reducing the system capacity. The communication system may provide communication services that include wireless radio transmission of digitized speech, still or moving images, text messages and other types of data. An encoder in a transmitter of the communication system may receive a packet of data for encoding. Each data packet may be transmitted in a time frame. The data rate of data transmitted in each packet may be selected based on one or more parameters. The teachings of issued U.S. Pat. Nos. 5,914,950 and 5,923,650, incorporated by reference herein, and assigned to the assignee of the present application for a patent, provide at least one method of reverse link data rate scheduling based on the system parameters.
Generally, the total reverse link capacity is limited by the total interference generated by the mobile stations. To control and minimize the interference, the transmit power level of the mobile stations is controlled by power control loops. The power level for the reverse link of each mobile station is controlled by an outer loop and an inner loop. The outer loop has a set point relating to the total energy per bit over noise plus interference ratio, Eb/(No+Io), or the total carrier energy over noise plus interference, Ec/(No+Io). The inner loop adjusts the set point based on the reverse link channel condition. The set point may be used for the calculation of the reverse link total load level. Generally, when the set point is set at a higher level, the reverse link power level is also set for a higher level. High power level is used to overcome the interference and noise in the propagation channel. Therefore, the set point is an indication of the power level transmitted by each mobile station. To calculate the load level, which has a direct correlation with the transmit power level, the set point may be used. The calculated reverse link total load level is used for the reverse link data rate scheduling. When the reverse link load level is high in comparison to a low load level, fewer number of mobile stations may receive reverse link data communication at high data rate.
The reverse link signal of the mobile station may be received at several base stations, but not necessarily if the mobile station is communicating or in a soft handoff condition with all the base stations. The signals received at such base stations add to the total reverse link load level. Therefore, the set point in the reverse link outer loop power control does not represent an accurate indication of the total load level.
To this end as well as others, there is a need for a method and apparatus to efficiently determine the reverse link load level for reverse link data rate scheduling in a communication system.